Hi Xavier, Thanks for attaching the cif file. You are right that I didn't consider any particular symmetry. I just built the structure with the known lattice parameters from the literature. I thought if I have correct structure I would get correct SCF result even if I don't take advantage of all available symmetry, even though it takes more time. Anyway, I will try with this structure now.
Best regards, Fhokrul ________________________________________ From: wien-boun...@zeus.theochem.tuwien.ac.at [wien-boun...@zeus.theochem.tuwien.ac.at] On Behalf Of Xavier Rocquefelte [xavier.rocquefe...@univ-rennes1.fr] Sent: Wednesday, December 23, 2015 6:54 AM To: A Mailing list for WIEN2k users Subject: Re: [Wien] Graphene bandstructure Dear Fhokrul Your structure looks strange to me. The angle is 60° and not 120° and it seems that you do not take benefit of the symetry. Here is a cif file of graphene based on the graphite structure in which I have simply increase the c parameter. The structure you are using may explain why you still have a gap (symetry problem). Best Regards Xavier #====================================================================== # CRYSTAL DATA #---------------------------------------------------------------------- data_VESTA_phase_1 _pd_phase_name 'C' _cell_length_a 2.45600 _cell_length_b 2.45600 _cell_length_c 15.00000 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _symmetry_space_group_name_H-M 'P 63 m c' _symmetry_Int_Tables_number 186 loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-y, x-y, z' '-x+y, -x, z' '-x, -y, z+1/2' 'y, -x+y, z+1/2' 'x-y, x, z+1/2' '-y, -x, z' '-x+y, y, z' 'x, x-y, z' 'y, x, z+1/2' 'x-y, -y, z+1/2' '-x, -x+y, z+1/2' loop_ _atom_site_label _atom_site_occupancy _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_adp_type _atom_site_B_iso_or_equiv _atom_site_type_symbol C1 1.0 0.000000 0.000000 0.000000 Biso 1.000000 C C2 1.0 0.333333 0.666667 0.000000 Biso 1.000000 C "Islam, Md F" <isl...@uta.edu> a écrit : > Sorry, in my earlier email, I meant to say with 30 x 30 x 1 mesh, gap > is smaller but > it doesn't close completely. > > Thanks, > Fhokrul > > > ________________________________________ > From: wien-boun...@zeus.theochem.tuwien.ac.at > [wien-boun...@zeus.theochem.tuwien.ac.at] On Behalf Of Islam, Md F > [isl...@uta.edu] > Sent: Wednesday, December 23, 2015 6:22 AM > To: A Mailing list for WIEN2k users > Subject: Re: [Wien] Graphene bandstructure > > Hi Prof Blaha, > > Here is the structure I am using. I tried to be as precise as > possible with position coordinates. > I think size of the vacuum is sufficiently large so that > supercell-supercell interaction is negligible. > So far what I have got is that with LDA xc if I use 25 x 25 x 1 > k-mesh there is a gap at the Fermi > level (which passes through K point) but if I use 30 x 30 x 1 k-mesh, > gap closes but DOS is not > zero at the Fermi level (about 0.001/eV). Please let me know if I am > doing anything wrong with > this calculation. > > > Thanks, > Fhokrul > > > Graphene > P LATTICE,NONEQUIV.ATOMS: 2 > MODE OF CALC=RELA unit=bohr > 4.647800 4.647800 30.000000 90.000000 90.000000 60.000000 > ATOM -1: X=0.00000000 Y=0.00000000 Z=0.50000000 > MULT= 1 ISPLIT= 8 > C NPT= 781 R0=0.00010000 RMT= 1.3200 Z: 6.0 > LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 > 0.0000000 1.0000000 0.0000000 > 0.0000000 0.0000000 1.0000000 > ATOM -2: X=0.66666667 Y=0.66666667 Z=0.50000000 > MULT= 1 ISPLIT= 8 > C NPT= 781 R0=0.00010000 RMT= 1.3200 Z: 6.0 > LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 > 0.0000000 1.0000000 0.0000000 > 0.0000000 0.0000000 1.0000000 > 12 NUMBER OF SYMMETRY OPERATIONS > -1-1 0 0.00000000 > 0 1 0 0.00000000 > 0 0-1 0.00000000 > 1 > -1-1 0 0.00000000 > 0 1 0 0.00000000 > 0 0 1 0.00000000 > 2 > -1-1 0 0.00000000 > 1 0 0 0.00000000 > 0 0-1 0.00000000 > 3 > -1-1 0 0.00000000 > 1 0 0 0.00000000 > 0 0 1 0.00000000 > 4 > 0 1 0 0.00000000 > -1-1 0 0.00000000 > 0 0-1 0.00000000 > 5 > 0 1 0 0.00000000 > -1-1 0 0.00000000 > 0 0 1 0.00000000 > 6 > 0 1 0 0.00000000 > 1 0 0 0.00000000 > 0 0-1 0.00000000 > 7 > 0 1 0 0.00000000 > 1 0 0 0.00000000 > 0 0 1 0.00000000 > 8 > 1 0 0 0.00000000 > -1-1 0 0.00000000 > 0 0-1 0.00000000 > 9 > 1 0 0 0.00000000 > -1-1 0 0.00000000 > 0 0 1 0.00000000 > 10 > 1 0 0 0.00000000 > 0 1 0 0.00000000 > 0 0-1 0.00000000 > 11 > 1 0 0 0.00000000 > 0 1 0 0.00000000 > 0 0 1 0.00000000 > 12 > > > > > ________________________________________ > From: wien-boun...@zeus.theochem.tuwien.ac.at > [wien-boun...@zeus.theochem.tuwien.ac.at] On Behalf Of Peter Blaha > [pbl...@theochem.tuwien.ac.at] > Sent: Tuesday, December 22, 2015 3:29 PM > To: A Mailing list for WIEN2k users > Subject: Re: [Wien] Graphene bandstructure > > The two eigenvalues at K must be identical by symmetry. > > If you have a splitting of some meV it means that your structure is > slightly wrong. > > Typical errors: positions of 1/3 and 2/3 must be given in full precision. > 0.3333 is NOT 1/3 > > Am 22.12.2015 um 20:31 schrieb Islam, Md F: >> Hi Prof Blaha, >> >> I have got the gap from plotting bandstructure as well as DOS >> calculations. >> I can see the linear dispersion at the K point just like the way it >> is suppose to be >> when I plot all the bands in eV range. But if I zoom in at the K >> point in meV range, >> I can see the gap. >> >> I don't think there is anything wrong with the structure. I did >> check all bond lengths, >> angles before I ran the calculations and they are correct. I suspect >> I may have to adjust >> parameters. I started to see some difference with LDA xc functional >> with larger k mesh. >> >> >> Thanks, >> Fhokrul >> >> >> >> >> ________________________________________ >> From: wien-boun...@zeus.theochem.tuwien.ac.at >> [wien-boun...@zeus.theochem.tuwien.ac.at] On Behalf Of Peter Blaha >> [pbl...@theochem.tuwien.ac.at] >> Sent: Tuesday, December 22, 2015 11:35 AM >> To: A Mailing list for WIEN2k users >> Subject: Re: [Wien] Graphene bandstructure >> >> Graphene is metallic by "symmetry", i.e. EF is at a 2-fold eigenvalue at >> the K-point and bands cross with a linear dispersion. >> >> From where do you know that graphene has a gap in your calculations ?? >> >> From :gap in the scf file or from plotting the bandstructure or ... >> >> It the state at K is not degenerate, you have the wrong symmetry and are >> not doing graphene. >> >> Am 22.12.2015 um 16:51 schrieb Islam, Md F: >>> Hi, >>> >>> I am trying to do a bandstructure calculation of graphene to >>> check if I can >>> reproduce results discussed in literature (I am using a unit cell >>> of 2 atoms). >>> With spin-orbit coupling, there should be a gap of the order of few >>> micro-eV >>> and without spin-orbit, there should not be any gap at Dirac point. >>> But I am >>> getting a gap of meV even without spin-orbit. I tried both GGA and LDA with >>> very dense mesh but the gap does not close. So I am wondering if anyone >>> have any suggestion about how to do it in Wien2k. >>> >>> >>> Thanks, >>> Fhokrul >>> _______________________________________________ >>> Wien mailing list >>> Wien@zeus.theochem.tuwien.ac.at >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>> SEARCH the MAILING-LIST at: >>> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >>> >> >> -- >> -------------------------------------------------------------------------- >> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna >> Phone: +43-1-58801-165300 FAX: +43-1-58801-165982 >> Email: bl...@theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at >> WWW: http://www.imc.tuwien.ac.at/staff/tc_group_e.php >> -------------------------------------------------------------------------- >> _______________________________________________ >> Wien mailing list >> Wien@zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> SEARCH the MAILING-LIST at: >> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> _______________________________________________ >> Wien mailing list >> Wien@zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> SEARCH the MAILING-LIST at: >> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html >> > > -- > -------------------------------------------------------------------------- > Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna > Phone: +43-1-58801-165300 FAX: +43-1-58801-165982 > Email: bl...@theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at > WWW: http://www.imc.tuwien.ac.at/staff/tc_group_e.php > -------------------------------------------------------------------------- > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > _______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html